The present invention relates to an organometallic complex, and more specifically to an organometallic complex used in an organic electroluminescent device.
Organic electroluminescent diode research began with Pope in 1962, providing single crystal luminescent naphthalene under application of an external voltage. A double-layer organic thin film device was then provided by Tan (Kodak Corporation) in 1982, significantly increasing brightness and luminescent efficiency and leading to follow-up research. Applications regarding organometallic complexes used in organic electroluminescent devices began in 1980, such as Pt(II), Ru(II), Os(II), Eu(III), and Ir(III) complexes, of which Ir(III) complexes were the most popular.
Initial doped red phosphorescent complexes were provided by M. E. Thompson and S. R. Forest as disclosed in Nature, 395, 1988, pages 151˜154, providing Pt as a metal center of a complex with a luminescent wavelength of 650 nm, quantum efficiency of 1.3%, and luminescent intensity of 0.15 lm/W under a current density of 100 cd/A. More types of Ir complexes were provided by M. E. Thompson in 2001 (J. Am. Chem. Soc. 2001, 123, 4304˜4312), with luminescent wavelengths across red, green, and blue light regions. In 2003, M. E. Thompson further provided a comparison of luminescent efficiency and lifetime between facial and meridional isomers of a Ir complex as disclosed in J. Am. Chem. Soc. 2003, 125, 7377˜7387. Other related technology is disclosed in U.S. Pre-Grant Pat. No. 2002024293, 2002034656, 2002045061, 2003017361, 2003092935, 2003102800, 2004053071, 2004102632, 2004086743, and 2004110031, in J. P. Pre-Grant Pat. No. 2002226495, 2002338588, 2003109758, 2003113246, 2003119179, 2003123982, 2003147021, 2003171391, 2003206320, 2003253128, 2003253129, 2003253145, and 2004111379, and in G. P Pre-Grant Pat. No. 2004026886, 2004028217, 2004037836, 2004048395, and 2004055130.
Various Ir complexes have been provided, such as Ir complexes coordinating with acetyl acetone as disclosed in E.P. Pat. No. 1434286 and a blue phosphorescent Ir complex with an emission wavelength exceeding 500 nm and quantum efficiency exceeding 5% as disclosed in U.S. Pat. No. 2002024293. Orange phosphorescent Ir complexes, however, have yet to be effectively provided, regarding compounds such as Bt2Ir(acac) with an emission wavelength of about 560 nm provided by Thompson as disclosed in J. Am. Chem. Soc. 2001, 123, 4304˜4312 and an orange phosphorescent Ir complex with emission wavelength of about 570 nm as disclosed in G.P. Pat. No. 2003040250.